Thermal, acoustical and/or vibrational abatement shields have been used in severe duty applications, such as in the engine compartment and exhaust tunnels of automobiles and trucks, to reduce transfer of heat, noise and vibration from within the engine compartment or exhaust tunnels into the passenger compartment of the vehicle. Since such shields are subjected to severe conditions, including high temperatures, substantial vibration, and road hazards, these shields must be ruggedly constructed in order to remain serviceable for, essentially, the life of the vehicle. Generally speaking, these shields are made of at least two metal foils sandwiching therebetween an insulation material. For the particular purpose of the shield, the insulation material may be a thermal insulation or an acoustical insulation or a vibrational insulation, or a combination of any two or all three thereof. For example, when the insulation is a glass fibrous batt, that fibrous batt functions as all of a thermal insulator, an acoustical insulator and a vibration insulator. On the other hand, when the insulation material is simply an air space between the two metal foils, the shield functions mainly as a thermal shield. When the insulation material is a high density material, such as impregnated glass fibrous material, the shield can function as a thermal shield and an acoustical shield, as well as have some vibrational insulation properties.
A problem in connection with these shields which has long plagued the art is that of adequately sealing peripheries of the shield sufficiently that the shield will remain sealed over its expected life, will essentially prevent the egress of water and other road contaminations into the interior of the shield, and can be produced in a convenient and economical manner. Various approaches for sealing the peripheries of such shields have been proposed in the art, and include adhesively bonding the peripheries of the shield with high temperature resistant glues, clamping the peripheries of the shield with specially designed clamping devices, and mechanically bending peripheries of the shield into some sealed configuration.
Adhesively bonding the peripheries is most convenient and economical, but under the severe conditions at which the shield operates, the adhesives, glues and the like often fail, and the shield becomes unserviceable by reason of, among others, egress of water into the interior of the shield.
Specialized clamps for clamping the periphery of the shield can be quite effective, and if properly constructed should remain serviceable for the life of the shield. However, such clamps are very expensive to manufacture and time consuming to apply to the shield and, hence, have not been adopted for usual shields of this nature.
Bending of peripheries of the shield to form a seal of the bent foils is an accepted practice, but seals formed by conventional bending techniques are prone to leakage and egress of water and other road contaminations. In addition, with such conventional bending techniques, the seal can be placed on a periphery which is disposed only at an outer edge of the shield. While this limitation has not been a serious limitation in the past, with more modern automobiles, these shields may have peripheries not just on the outer edges thereof but at apertures and other discontinuities in the shield in order to accommodate special provisions for the closely spaced components of modern automobiles. Accordingly, prior art conventional bending techniques of the metal foils of the shield for producing such seals of the shield are no longer applicable to increasing numbers of applications of these shields in modern automobiles.
The art has provided a number of approaches for bending metal foils into a sealed configuration, and for a wide variety of purposes. For example, U.S. Pat. No. 1,206,487, issued in 1916, discloses bending flanges of metal barrels to form chimes on the barrels. In that approach, a barrel head with a flange is fitted into a body of the barrel. By cold rolling, a grooved depression is made between the barrel body and the flange. Thereafter, by compressing the barrel body and flange, the grooved depression is collapsed until the walls of the grooved depression are bent back upon themselves, forming something of a "T"-shaped fold.
U.S. Pat. No. 4,632,592, issued in 1986, shows punching a configuration into two metal foils so as to provide a tubular portion of the two metal foils and then compressing that tubular portion to form something of a "Z"-shaped configured seal.
U.S. Pat. No. 4,760,634, issued in 1988, shows a somewhat similar seal to that of the immediately above-mentioned patent, but discloses the use of a die in forming such a seal. In the method, an upper die passes into a lower die and through metal foils so that a tang of the die penetrates into a bore of the die. During that penetration, the metal of the foil is thinned, and the metal flows in a somewhat "Z"-shaped configuration. U.S. Pat. No. 4,831,711, issued in 1989, shows a somewhat similar approach.
U.S. Pat. No. 4,897,912, issued in 1990, also shows an approach of forming a seal with a die-pressing operation similar to the above-discussed patent. However, in that method, a die and an anvil operating within a die cavity cause deformation of peripheral edges of the joint which is said to increase the strength of the resulting clinch joint. That clinch joint is, again, something of a "Z"-shaped joint.
A similar "Z"-shaped joint is also shown in U.S. Pat. No. 4,910,853, issued in 1990, and U.S. Pat. No. 5,155,897, issued in 1992, shows a similar type joint.
U.S. Pat. No. 5,230,136, issued in 1993, shows a variation of that "Z"-shaped joint, where lateral channels or protrusions may be made in the punched joint.
Finally, U.S. Pat. No. 5,517,743, issued in 1996, shows forming a "Z"-shaped joint by use of a downwardly moved die and an upwardly moved punch.
However, all of these approaches suffer from common disadvantages. First of all, the "Z"-shaped seals, while usually quite effective in maintaining the mechanical structural integrity of the shield, are subject to leakage and especially egress of water into the shield. Secondly, because of the manner in which these "Z"-shaped seals are produced, it is generally not possible, or at least impractical, to attempt forming such seals at a perimeter on the interior of the shield, for example, the perimeter around an aperture in the shield. Thirdly, the process of producing these "Z"-shaped seals are generally fairly complex and are not economical to operate.
Accordingly, it would be of substantial advantage to the art to provide a method of producing a thermal, acoustical and/or vibrational abatement shield which avoids the disadvantages of the prior art and a thermal, acoustical and/or vibrational abatement shield which also avoids the disadvantages of the prior art, as noted above.